In recent years, in electronic devices such as portable information terminals, modules produced for respective functions are often combined and mounted on a board. Thus, high functionalization in electronic devices has been developed rapidly. From the point of view about resource saving and portability, reduction in thickness and weight of electronic device is required.
However, a printed wiring board such as a glass epoxy board forming an electronic circuit has a flat structure, and there is also a restriction in the mounting form of electronic components. It is therefore difficult to attain higher functionalization and more significant reduction in thickness and weight simultaneously.
MID (Molded Interconnected Device) technology for forming an electric circuit directly in the surface of an injection-molded article has been highlighted under such background. The MID technology can provide a mechanical function as a mechanism part and an electric function as a wiring circuit board for a module board to be mounted with modules. According to the MID technology, it is therefore possible to achieve smaller size of an electric device and higher accuracy of a module board including the electric device simultaneously, and it is further possible to reduce the number of assembling man-hours of the module board.
In addition, it has been considered that an electric device such as a portable terminal or a tablet terminal is mounted with a touchless motion function as an example of a proximity sensor. The touchless motion function is a function by which, for example, vertical or horizontal motion of a hand of a user on a display of an electronic device such as a portable terminal or a tablet terminal can be detected even though the hand of the user does not touch the display.
There has been already provided a light receiving element which is mounted with a driver for driving three LED elements as light emitting portions so as to implement a touchless motion function. FIG. 12(A) is a view for explaining an operation for detecting horizontal motion of a hand of a user in a background-art touchless motion function. FIG. 12(B) is a view for explaining an operation for detecting vertical motion of the hand of the user in the background-art touchless motion function. FIG. 12(C) is a graph for explaining signal strength of reflected light in response to the horizontal motion of the hand of the user. FIG. 12(D) is a graph for explaining signal strength of reflected light in response to the vertical motion of the hand of the user. FIG. 12(E) is a chart for explaining light emitting timings of respective Ir-LEDs 101, 102 and 103.
As shown in FIG. 12(A), three near infrared light emitting elements (Ir-LEDs) 101, 102 and 103 are disposed in an upper portion of a portable terminal 100 and inside a housing of the portable terminal 100 so as to form an angle of 90° with respect to the lateral and longitudinal directions of the paper of FIG. 12(A). In addition, as shown in FIG. 12(A), in the upper portion of the portable terminal 100 and inside the housing of the portable terminal 100, a light receiving element 105 is disposed between the two lateral Ir-LEDs 101 and 102.
The three Ir-LEDs 101, 102 and 103 emit light in a time division manner so as to have a light emitting cycle of 10 ms to 2,000 ms and variable light emitting timings as shown in FIG. 12(E). When a user's hand 106 moves from right to left with respect to the portable terminal 100 as shown in FIG. 12(A) and FIG. 12(C), the light receiving element 105 receives reflected light derived from light emitted in a time division manner from the two Ir-LEDs 102 and 103 located on the right side. A little later, the light emitting element 105 further receives reflected light from the other Ir-LED 101 located on the left side. The horizontal motion of the user's hand 106 can be detected due to the deviation of the light reception timing.
In the same manner, when the user's hand 106 is moved downward with respect to the portable terminal 100 as shown in FIG. 12(C) and FIG. 12(D), the light receiving element 105 receives reflected light derived from light emitted in a time division manner from the two Ir-LEDs 101 and 102 located on the upper side. A little later, the light emitting element 105 further receives reflected light from the other Ir-LED 103 located on the lower side. The vertical motion of the user's hand 106 can be detected due to the deviation of the light reception timing.
As a prior technique related to a proximity sensor, there has been known a light receiving and emitting integrated element array which includes a board, a plurality of light receiving elements disposed in a column on the board, and a plurality of light emitting elements disposed in a column so that a plurality of ones of the light emitting elements can be provided correspondingly to each light receiving element (for example, see Patent Literature 1). The light receiving and emitting integrated element array detects the position of an object to be detected, based on the magnitude of reflected light (magnitude of photocurrent) from the object to be detected in response to light from the light emitting elements provided in a column.